Rotary core drill



Dec. 16, 1952 c. c. BROWN ROTARY CORE DRILL 2 $HEETSSHEET 1 Filed Jan. 30, 1948 FIG. 3-

0. 6. BROWN IN V EN TOR.

Dec 16, 1952 c. c. BROWN 2,621,897

ROTARY CORE DRILL Filed Jan. 30, 1948 2 SHEETS-SHEET 2 t M FIG. 8

i I m5 F g G 6 a. 0. snow/v IN V EN TOR.

ATTORNEY Patented Dec. 16, 1952 EFWE 6 Claims.

This invention relates to improvements in rotary core drills.

Rotary core drills conventionally comprise a pair of concentrically arranged tubular barrels, the outer one of which carries an annularly shaped bit at its lower end adapted to out a cylindrical core from the earth formations being traversed, the core being received in the inner barrel and retained therein for withdrawal from the well. The outer barrel of such core drills is normally made of a diameter which is only very slightly less than the diameter of the bore hole being drilled and is of substantial length, for example, to 90 feet. The close clearance for such substantial lengths subjects conventional core drills to considerable danger of becoming stuck in the bore hole and this is a very frequent occurrence with such drills. As a result, twistoffs and loss of the core drill and core are quite frequent occurrences, necessitating frequent fishing jobs and side tracking of the lost tools in many cases, all of which is expensive and time consuming, particularly in the drilling of deep wells.

Normally it is only the outer barrel which becomes stuck but in the conventional forms of comes stuck in a well bore, it is not only diiilcult to fish out but is difficult to drill out because of the considerable amount of heavy metallic equipment comprising both the inner and outer barrels of the structure. On the other hand, if it were possible to remove the inner barrel from the core drill after it becomes stuck, it would be a relatively easy matter to drill out or cut up the outer barrel which is generally no more than a length of steel pipe, and continuation of the drilling could be then accomplished without too much trouble.

Accordingly, it is a principal object of the present invention to provide an improved form of core drill whereby the inner barrel may be selectively removed and withdrawn from the outer barrel when the latter becomes stuck in a well.

Another object is to provide an improved form of core drill wherein both barrels are connected to drilling string by means of a safety joint, which is arranged to permit selective withdrawal of the inner barrel.

Other and more specific objects and advantages of this invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings which illustrate useful embodiments in accordance with this invention.

In the drawings:

Fig. 1 is a more or less diagrammatic view showing the core drill, in accordance with this invention, disposed in a well bore and illustrating the connection of the inner barrel to the drilling string as it is withdrawn from the outer barrel;

Figs. 2 and 2a comprise a longitudinal sectional view of a core drill in accordance with this invention;

Fig. 3 is a longitudinal sectional view of the lower end of the core drill modified to illustrate another embodiment in accordance with this invention;

Fig. 4 is a quarter-sectional longitudinal view of the upper portion of another embodiment in accordance with this invention, employing another form of coupling between a core drill and a drilling string; and

Figs. 5, 6, 7, and 8 illustrate details of the modified coupling shown in Fig. 4.

Referring to the drawings, the core drill in accordance with one embodiment of this invention, comprises a tubular outer barrel I0 enclosing a concentrically arranged inner barrel II spaced therefrom by an annular space I 2. The lower end of outer barrel H) has connected thereto a bit [3 of generally annular form and provided with cutting elements M about the lower faces of the bit. The bit is connected to the outer barrel in the more or less conventional manner through a threaded shank I5 engageable with complementary threads on the lower end of outer barrel Ill. Bit l3 has the conventional central passageway it through which the core being cut thereby enters the interior of the drill. Bore ll of shank I5 is tapered upwardly and outwardly to form a tapered seat on which is slidably mounted a ring shaped core catcher is, which is slit longitudinally on one side at l9 and is provided with inwardly and upwardly extending circular teeth 20. The upper end of inner core barrel H is closed by means of a head 21 through which extends a fluid passageway 22 providing communication between the interior of inner barrel H and annular space i2. Extending upwardly from head 2| is an elongated shank 23 which extends into a tubular housing 24 in which the upper end of shank 23 is rotatably mounted on suitable roller bearings 25, mounted between housing 24 and the upper end of shank 23 to form a swivel connection between these members. Packing cups 28 form fluid tight seals between housing 24 and the body of shank 23 below bearings 25. A pressure lubricant fitting 28 extends through the wall of housing 24 from the exterior thereof and is arranged for the introduction of a suitable lubricant or grease into the interior of housing 24 to fill the interior of housing 24 with lubricant which serves to lubricate the swivel connection and to form a fluidtight seal between the housing and shank 23.

Rigidly connected to the upper end of outer barrel I0, is a hollow box portion 23, internally threaded at 30, to receive a pin member 3!, having external threads 32 engageable with threads 30 of the box member. Box portion may be connected to outer barrel 50 in any suitable manner, as by means of a threaded connection indicated at 21, by welding, or may be formed as an integral part of outer barrel E3. The lower end of pin member 3| is rigidly connected to a hollow socket 36 which is threadedly connected to the upper end of housing 24 and forms a closure therefor. The upper end of pin member 3| is provided with an internally threaded box portion 33 for attachment of the device in the usual manner to a conventional hollow rotary drilling string 38 (Fig. 1). Pin member Si is provided with the usual hollow bore as communicating with the interior of box 33 and the registering bore of the drilling string connected thereto. A plurality of fluid passageways 35 extend generally laterally through the lower end of pin member 23 to the exterior thereof above socket 36 and provide communication between passageway 34 and annular space i2. Suitable pressure seals, such as O-rings 3"! re provided between the contacting surfaces of pin and box members 3| and 29, respectively, above and below the threaded connection there-between, to seal this threaded connection against the entry of fiuid or detritus. Pin member 3| and box member 29 constitute a joint, conventionally referred to in the drilling art as a safety joint, which is a form of coupling for pipes or the like, arranged for relatively easy separation into its constituent members. There are numerous forms of safety joints well-known to those skilled in the welldrilling art and the form illustrated is of a conventional type in which the engaging threads 33 and 32 are of the square helical form which are non-seizing, irrespective of the degree of torque applied and are, therefore, more readily separable under an unscrewing torque than the standard tool joint threads normally employed for coupling the sections of the drill pipe.

The above described device is employed in the following manner. Pin member 3!, which is directly attached to inner barrel I through housing 24 and the swivel connection to shank 23, in the manner above-described, is connected by means of box portion 33 to the lower end of a hollow drilling string 38 in the usual manner and the inner barrel is then inserted in outer barrel [0 and screwed thereto by the engagement of threads 32 with threads of the box member 29. The drill, thus attached to the end of drilling string 38, is then lowered into the well bore B and drilling begun in the usual manner by rotation of drilling string 38. Drilling fluid of conventional character will be pumped through the interior of the drilling string and will pass through passageways 34 and 35 into annular of the bit and into the interior of inner barrel 1 l. Fluid passageway 22 permits the escape into the annular space l2 of any fluid trapped in the interior of inner barrel I I between the upper end of the entering core and closure 2!. It will be understood that when the core enters inner barrel ll, frictional engagement therebetween will cause the latter to remain stationary while the outer barrel rotates with the drilling string. Ihe described swivel connection between shank 23 and housing 24 permits this relative rotation to occur.

If the drilling proceeds normally, when cor of a length sufficient to fill inner barrel H ha been cut, the drilling string will be jarred or manipulated in any conventional manner to break the core loose from the formation from which it is being cut, whereupon the drilling string will be withdrawn from the well carrying the entire core drill and core with it. The core will, of course, be seized by the toothed catcher l3 and will be held in the interior of the drill while the tools are being withdrawn from the well.

However, in the event outer barrel it) becomes stuck in the well, which, as noted above, is a frequent occurrence in this type of drilling, the drilling string will be rotated in the counterclockwise direction in order to unscrew pin member 3| from box member 29. Because of their special form these threads will unscrew preferentially over the other threaded connections in the drilling string. When this operation is completed, drilling string 38 can be withdrawn from the Well and because of the described connection between pin member 3! and inner barrel i I, the drilling string will bring with it inner barrel H and leave only the outer barrel E3 in the well. If the core has not been broken loose at this time, inner barrel will simply be drawn upwardly over the core leaving the latter in the well. Any suitable and conventional method can then be employed to either fish out the outer barrel or, if necessary, to cut it up or otherwise remove it in order that drilling may proceed. If the outer barrel cannot be recovered from the well, it is only necessary to replace this part of the drill in order to reconstitute the complete structure for further drilling.

Fig. 3 illustrates a slightly modified form in which the lower end of inner barrel H is provided with a short tubular extension G0, having a downwardly and inwardly sloping surface M, on which a core catcher 42 of the same form as core catcher [8, but of smaller diameter, is slidably mounted. This arrangement is provided to assure the withdrawal of the core with the inner barrel at any time it becomes necessary to withdraw the inner barrel alone when the outer barrel has become stuck.

Figs. 4 to 8 inclusive, illustrate another embodiment of a core drill in accordance with this in vention, wherein a modified type of safety joint is employed for coupling the core drill to the drilling string. In this embodiment box member 29 and pin member 3| are provided with a section of right-hand complementary threads 39 and 32, respectively, as in the previously described embodiment. The upper end of box member 29 above the section of threads 33 is bored out to a somewhat enlarged internal diameter and this enlarged portion of the bore of box member 23 is internally threaded with a group of left-hand threads 39. The section of the body of pin member 3| opposite left-hand threads 39 is machined to a smooth cylindrical surface, indicated at 40. The upper end of surface 40 is machined to provide an upwardly and outwardly tapering seat 4| which extends to the exterior of pin member 3| at a point above the upper end of box member 29. A collar member 42, externally threaded with left-hand threads 43 matching threads 39, is adapted to be screwed inside the upper end of box member 29 in the space between threads 39 and surface 50. The relative diameters of surface 40 and the interior of collar member 12 are such as to provide clearance between these surfaces when the collar member is screwed into box member 29. The upper edge of collar member 42 has an outwardly turned bead M, the inner surface of which is tapered to complement seat 3!. The lower edge of bead 44 is undercut to form a seat 45 for reception of a sealing gasket 46 which is adapted to be interposed between bead a4 and a the upper end of box member 29.

With this form of safety joint, even more posi tive preferential breaking of the joint between pin member 3! and box member 29 is assured when the drilling string is rotated in a direction to unscrew these members. With collar member 42 inserted between the pin and box members and connected to the latter by means of the left-hand threads 3943, when rotation of the drilling string is in the normal or right-hand direction, collar member 42 will tend to unscrew and move upwardly against seat 4! and thereby limit the degree of tightness to which threads 30 and 32 may be made up thereby preventing seizure between these threads. The contacting surfaces of seat ll and bead 44 will be machined to a non-seizing angle, for example, 10 degrees, so that these surfaces will not seize irrespective of the degree of torque exerted on the drilling string. When the drilling string is rotated in the reverse or unscrewing direction, collar member 42 will tend to screw into box member 29 and thus will break away from its contact with pin member 3| instantaneously upon the first unscrewing movement of the pin member. Gasket 46, in addition to forming a seal for threads 39-43 also will form a compressible cushion which will permit sufiicient degree of downward movement of collar member 42 in box member 29- to efiect the described break in the safety joint.

From the foregoing, it will be seen that the core drill in accordance with this invention comprises the combination of a safety joint with the inner and outer barrels of a more or less conventional core drill for connecting both the barrels to a drilling string in such a manner as to permit selective withdrawal of the inner barrel when necessary.

It will be understood that bit !3 may be of any of the several conventional forms of core bits.

It will also be understood that various changes and alterations may be made in the details of the structure in accordance with this invention within the scope of the appended claims but 6 without departing from the spirit of this invention.

What I claim and desire to secure by Letters Patent is:

1. A rotary core drill, comprising, an outer core-cutting barrel, an inner core-receiving barrel, a safety joint adapted to connect both said barrels to a drilling string, said safety joint comprising a pin member adapted to connect said inner barrel directly to said drilling string and a box member threadedly connecting said outer barrel to said pin member, said pin and box members having threaded sections at their re spective inner ends composed of cooperating right-hand threads of the non-seizing type, said pin member having a non-threaded portion adjacent the base of its threaded section and an external shoulder at the outer end of said nonthreaded portion, said box member having opposite said non-threaded portion, a second threaded section composed of left-hand threads, and a collar inserted between said non-threaded portion and said second threaded section, said collar having external left-hand threads engageable with the threads of said second threaded section and having an outwardly extending flange at its upper end compressively engageable between said shoulder and the outer end of said box member.

2. In a rotary core drill according to claim 1, a compressible packing ring disposed between said flange and said outer end of said box member.

3. A rotary core drill according to claim 1 wherein a core-catching means is mounted in the lower end of one of said barrels.

4. A rotary core drill according to claim 1 wherein a core-catching means is mounted in the lower end of said outer barrel.

5. A rotary core drill according to claim 1 wherein a core-catching means is mounted in the lower end of said inner barrel.

6. A rotary core drill according to claim 1 wherein a core-catching means is mounted in the lower end of one of said barrels, said corecatching means comprising a downwardly and inwardly tapering internal seat, and a correspondingly tapered core-gripping collar longitudinally split at one point slidably disposed on said seat.

CICERO C. BROWN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 790,331 Terry May 23, 1905 1,720,700 Stone July 16, 1929 1,982,915 Jenks Dec. 4, 1934 2,128,914 Burke et al Sept. 6, 1938 2,189,923 Phipps Feb. 13, 1940 2,403,002 Johnson July 2, 1946 2,551,995 Brown May 8, 1951 

